Dental appabattts



April 17, 1928.

M. A. SPARKS DENTAL APPARATUS Filed April 9. 1927 2 Sheets-Sheet l I N V EN TOR.

A TTORN EY Patented Apr. 1'7, 1928.

` DENTAL APPARATUS.

Application mea Aprn 9, 1927. seriai'no. 182,495.

My invention relates broadly to dental apparatusand more particularly to a plaster trimmer for use in the shaping oi patterns in the preparation of dentures.

One of the objects ot my invention is to providea constructionof cutter for working various grades of plaster some of which become very hard after setting wherein the model being operated upon may be sup ported `upon an angularly disposed desk-like platform upon whichthe `pattern may be moved to various positions beneath a cooperating plaster cutter and readily shaped to the desired size.

Another object of my invention is to pr0- vide a. construction of plaster trimmer and cooperating tray whereby all particles which are moved from the model being operated upon maybe retained in the t-ray and removed from the trimmer2 the tray remaining in a horizontal position at alltimes.

Still another object of my invention is to provide a vconstruction of cutter arranged to be mounted upon a plaster trimmer table where the pattern may be disposed at a substantial angle to the horizontal during the trimming operation `and whereby considerable force may be applied to the cutting operation of the trimmer with a positive stop arranged to limit the movement of the cuttingv blade.

A. further object of my invention is to provide a` construction of combined plaster trimmer and tray wherein an interlocking and spring pressed connection may be et tected between the tray and the plaster trimmer, the tray connecting `with one side of the plaster trimmer `by means of interlocking lugs and a spring` engagement device by which the tray may be automatically snapped into `and retained in position'with respect to the trimmer and readily removed therefromvfordispensing the particles which may be cut from the pattern which is being shaped. 4

Other and further objects of my invention reside inthe construction and arrangement `of parts of the plaster trimmer as will be more .fully set Jforth in the specification hereinafter following by reference to the accompanying drawing in which Figure 1 is a plan View showing` the plaster trimmer and tray attached thereto;`

Fig 2 is a side elevation showing the comn bined plaster trimmer and tray; Iig. 3 is g -11,666.316" UNITED STATES rATEN'T OFFICE, l

MANLEY A. SPARKS, OF ATLANTA, GEORGIA.

a cross-sectional view through the vplaster trimmer and tray taken on line 3--3-of Fig. 2; Fig. et is a fragmentary plan viewv of the tray locked into position with respect to the plaster trimmer; Fig.y 5 is a fragmentary view or' the plaster tray about to be removed lustrating the tray and showing the standing lugs by which the removable connection vis established with the plaster trim- Heretofore in the practice of dentistry has been customary tol shape the patterns in formingdentures by the use of hand toolsv and a sharpsblade has kbeen necessary in this work7 and by reason of the hardness of the plaster with which'it isnecessary to work,

`considerable force must be applied tothe blade. Such hand tools have proven veryy dangerous and have resulted in bad knife" wounds dur-ey to the slipping of the knife under heavy pressure. i I have devised the present plaster trimmer for eliminating the danger ot slippage cfa knifepin the shaping of the plasterpattern and at the same time provided meansfor securing the necessary pressure under which a blade must be moved with respect to the plaster pattern for shaping the pattern. The plaster on which the trimmer of: my invention operates is known `as syntheticstone or artificial stone, which materialf. becomes very hard` and diiiicult to f work.

With thel arrangement of the desk-like, platformV in the plaster trimmer of my invention, however, the plaster patterns `may. begmoved about to selected positions and' pressure applied tothe cutting knife for shaping the `plaster pattern to desired size. The excess plaster which `is Vtrimmed from the model is deposited in a movable tray adjacent the trimmer. This tray is locked with respect to the trimmer by a spring device which* enablesr the tray to move both longitudinally and laterally with respect to the trimmer for establishing a close `interlocking fit therewith, insuring the deposit of all the trimmed material into the tray. The tray is so shaped with respect to the frame of the trimmer that the tray flts beneath the trimmer and thereby receives all of the excess material. The spring device Vconstantly urges the tray into more intimate interlocking relationship with the trimmer, as will be more fully hereinafter described.

Referring to the drawings in more detail, reference character 1 designates the base of the trimmer ivliicli is provided `with an angularly disposed desk-like surface 2 for receiving the model or pattern which is being operated upon. rlhe base 1 has an upstanding supporting member 3 thereon to which is journaled as represented at 11 the lever knife 5. The lever is shaped as represented in Fig. 2, providing a. relatively Wide body portion 6, having a pair of guides .7 and 8 thereon, between which the cutting blade 9 is positioned. 'llhe cutting blade 9 is adjustable by means of screw device 10 operating in slots11.y 'The base 1 has a shortened edge portion as represented at 12, the edge portion 12 being provided withia pair of vertically extending apertures 14 and 15 which are arranged to cooperate with upstanding lug men'ibers1 and 17 on the tray 18. The tray 18 is more clearly represented in l? ig. 8 as having relatively high upstanding sides 19 tapering to the low side portions 20 and 21. low to pass beneath the lower edge 12 of the plaster 'trimmer body 1.V It becomes highly desirable to eliminate the tipping of the tray When attaching tray'to the trimmer or removing the tray from thetrimmer. This is accomplished by the arrangement illustrated in the drawing Where a spring device 22 is provided attached to one corner of the tray 18 wit a resilient portion 23 arranged to engage theV side of the trimmer 1. When interlocking the tray with the trin'imerasl illustrated in Fig. 6 the tray has the upstanding lugs 16 and 17 aligned With the apertures 15 and la. The tray is passed for- Ward toward the trimmer in such manner that the lugs land 17 pass Wholly through the apertures 15 and 14, the spring device 23 being subject-ed to compressional forces. lThe tray is then moved longitudinally with respect to the trimmer in such manner that the lugs abut with the corner surface of one wall of the plaster trimmer as illustrated in Fig. i until a vposit-ion is reached as illustrated in liig. 4 wherein the end of the spring 23 tends to force the tray continuously into tight engagement with the Walls of the trimmer by a resolution of both 1ongitudinally and laterally extending forces. Removal of the tray may be effected by a reversal of the hereinbefore ldescribed process as represented by the arrow in Fig. 5. By reason of the fact that the tray 18 extends beneath the plaster trimmer'there is 'lhe side portion 21 is su'liiciently Leeaeie no possibility of the cuttings falling out-- side of the tray. The tray may be removed Without tipping so that loss of the particles in the tray due to the low sides 20 and 21 avoided.

The plaster trimmer may be formed with a removable edge portion 24 for cooperation with the removable blade 9. The frame of the trimmer is so shaped as toy avoid deep corners, crevices and other places Where dust or moisture might accumulate.

For the purpose of facilitating Work on plaster models, I have found that a 30o angle is desirable for the desk-like surface 2, the surface being angularly disposed toward the operator. 1t will be observed that the cutter blade 9 is relatively narrow and is positioned at approximately the center of the length of the operating handle 25 for enabling the desired pressure to be placed upon the knife during the cutting operation. The plaster trimmer of my invention has proven to be highly practical in operation, and While l have described the invention in one of its preferred embodiments, I desire it tO be understood that modifications may be made and that no limitations upon my inveution are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent' of the United States is as follows:

1. Dental apparatus comprising a plaster trimmer having a supporting body portion,- a tray arranged to be brought adjacent the supporting body portion of said `plaster trimmer, and means for interlocking said tray with the supporting body portion of said plaster trimmer, said-means comprising a pair of upstanding lugs arranged to engage one side of the supporting body portion for forcing said lugs into engagement With the supporting body portion of said plaster trimmer.

2. Dental apparatus comprising a plaster trimmer having an inclined desk-like sup- `ot said plaster trimmer, and spring means porting surface, a cutting knife pivotally mounted adjacent the uppermost extremity of said supporting surface and adjacent one side thereof, a tray arranged to be moved in a horizontal direction for interlocking engagement with the side of said supportingv surface, and springV means for maintaining said tray in interlocking relationship With said plaster trimmer.

3. Dental apparatus comprising a supporting member having an angularly disposed supporting surface, a cutting knife ournaled from a position adjacent the upper extremity of said supporting surface, the side of said supporting member being shortened to permit the horizontal movement of one side of a tray member thereunder, said tray member being providedy With upstanding lugs on the side thereof which is adapted to be moved beneath the said side of said plaster trimmer, said plaster trimmer being apertured to permit the interlocking relationship of said lugs with the said side of said plaster' trimmer.

4. A dental apparatus comprising a plas# ter trimmer including a support, a desk like working surface angularly disposed on said support, a pivotally mounted cutter mounted at one side of said support for cooperation with said working surface, said support terminating immediately below said cutter above the lowermost extremity of said plaster trimmer, a tray having two relatively low sides and a rear relatively high side, with the fourth side thereof tapering from saidrear high side to the opposite low side, upstanding` lugs on the lo7 side of said tray which is arranged to fit under said plaster trimmer, said plaster trimmer being aper tured to permitthe interlocking engagement with the lugs on said tray.

5.`Dental apparatus comprising a plaster trimmer including a supportingfmembenan angularly disposed working surface Carried by said supporting member, a pivotally mounted cutter positioned atl one side of said supporting member for cooperation with Said Working surface, said supporting member being out away below said cutter, and

a tray vhaving one side thereof shaped to be moved horizontally beneath said' supporting i member to an overlapping position with respeet to the cut away side of the said supporting member, and spring means carried by Said trayL for establishing an interlocking relation between said tray and said trimmer.

In testimony whereof I affix my signa ture.

MANLEY A.` SPARKS. 

